Self-setting urethane adhesive paste system

ABSTRACT

An adhesive paste composition containing in admixture a resin component, a hardener component, a hydrophobic filler component and a curing agent. The resin component includes a polyol having at least two hydroxyl groups and the hardener component includes a liquid polyisocyanate containing at least two isocyanate groups. The admixture may be made by mixing together a premixed resin component containing a filler and a catalyst and a premixed hardener component containing a hydrophobic filler. The filler in the resin component, the hardener component, or both may be a thixotropic agent.

TECHNICAL FIELD

The present invention relates to adhesive paste compositions, and tomethods for making, curing and using such adhesive paste compositions.The paste compositions of the present invention are especially usefulfor bonding together foundry shapes, such as cores and molds, so as toassemble these shapes into a molding assembly for casting liquid metals.These paste compositions are particularly advantageous in their ease ofapplication to foundry shapes, and in the control that they provide overthe gel time in which the foundry shapes must be assembled together andthe short curing times before this molding assembly can be used forcasting a metal. More particularly, the invention relates to atwo-package or three-package adhesive system that can be readily mixedand applied on site. When these components are mixed, the resultingpaste is a true chemically-curing adhesive exhibiting rapid chemicalcuring requiring no heat and no extended drying times to achieve a hightensile strength cure.

BACKGROUND OF THE INVENTION

U.S. Pat. Nos. 3,409,579 and 3,676,392 disclose binder compositions foraggregate mixtures such as foundry mixes for making cores, molds andother foundry shapes for casting metal. The entire contents of each ofthese U.S. patents are incorporated herein by reference. These bindercompositions may be supplied as two-package systems comprising a resincomponent in one package and a hardener component in the other package.The resin component comprises an organic solvent solution of phenolicresin. The hardener component comprises a liquid polyisocyanate havingat least two isocyanate groups per molecule. At the time of use, thecontents of the two packages may be combined first and then mixed withthe sand aggregate, or preferably the packages are sequentially admixedwith sand aggregate. After a uniform distribution of the binder on thesand particles has been obtained, the resulting foundry mix is moldedinto the desired shape for subsequently casting a metal shape.

In U.S. Pat. No. 3,409,579, the molded shape is cured by passing agaseous tertiary amine through it. In U.S. Pat. No. 3,676,392, curing iseffected by means of a base having a pK value in the range of about 7 toabout 11 as determined by a method described by D. D. Perrin inDissociation Constants of Organic Bases in Aqueous Solution(Butterworths, London 1965). The base is introduced originally into theresin component before it is mixed with hardener, or it may beintroduced as the third component of a three-package binder systemcomprising in separate packages the resin component, the hardener, andthe base.

In both U.S. Pat. Nos. 3,409,579 and 3,676,392, the preferred phenolicresins contain benzylic ether resins along with other reaction products.Benzylic ether resins are condensation products of a phenol with analdehyde where the phenol has the general formula: ##STR1## wherein A,B, and C are hydrogen, hydrocarbon radicals, oxyhydrocarbon radicals, orhalogen, and where the aldehyde has the general formula R'CHO wherein R'is a hydrogen or a hydrocarbon radical of 1 to 8 carbon atoms, preparedin the liquid phase at temperatures below about 130° C. in the presenceof catalytic concentrations of a metal ion dissolved in the reactionmedium. The preparation and characterization of these resins isdisclosed in greater detail in U.S. Pat. No. 3,485,797, the entirecontents of which is incorporated herein by reference. The phenolicresin component of the binder composition is, as indicated above,generally employed as a solution in an organic solvent.

The second component or package of the binder composition comprises analiphatic, cycloaliphatic, or aromatic polyisocyanate having preferablyfrom 2 to 5 isocyanate groups. If desired, mixtures of polyisocyanatescan be employed. Less preferably, isocyanate prepolymers formed byreacting excess polyisocyanate with a polyhydric alcohol, e.g., aprepolymer of toluene diisocyanate and ethylene glycol, can be employed.Suitable polyisocyanates include the aliphatic polyisocyanates such ashexamethylene diisocyanate, alicyclic polyisocyanates such as4,4'-dicyclohexylmethane diisocyanate, and aromatic polyisocyanates suchas 2,4- and 2,6-toluene diisocyanate, diphenylmethane diisocyanate, anddimethyl derivatives thereof. Further examples of suitablepolyisocyanates are 1,5-naphthalene diisocyanate, triphenylmethanetriisocyanate, xylylene diisocyanate, and the methyl derivativesthereof, polymethylenepolyphenyl isocyanates,chlorophenylene-2,4-diisocyanate, and the like. Although allpolyisocyanates react with the phenolic resin to form a cross-linkedpolymer structure, the preferred polyisocyanates are aromaticpolyisocyanates and particularly diphenylmethane diisocyanate,triphenylmethane triisocyanate, and mixtures thereof.

The polyisocyanate is employed in sufficient concentrations to cause thecuring of the phenolic resin. In general, the polyisocyanate will beemployed in a range of 10 to 500 weight percent of polyisocyanate basedon the weight of the phenolic resin. Preferably, from 20 to 300 weightpercent of polyisocyanate on the same basis is employed. Thepolyisocyanate is employed in liquid form. Liquid polyisocyanates can beemployed in undiluted form. Solid or viscous polyisocyanates areemployed in the form of organic solvent solutions, the solvent beingpresent in a range of up to 80% by weight of the solution.

The bench life of an aggregate binder can be defined as the maximumpermissible time delay between mixing the binder components togetherwith an aggregate such as sand and the production of acceptable productstherefrom by at least partial curing. In order to extend the bench lifeof the above binder systems before they are contacted with the catalyticcomponent, various materials have been suggested. Phthaloyl chloride,acid halides, phosphorus compounds and other bench life extenders arecurrently being commercially employed for such purposes. Greatimprovements in bench life have been obtained through the use ofphosphorus halides as described in copending application Ser. No.575,208, now U.S. Pat. No. 4,540,724, and phosphorus based acids asdescribed in copending application Ser. No. 599,106 now U.S. Pat. No.4,602,069.

Attempts have been made in the past to use adhesive compositions similarto the foregoing binder compositions to bond together foundry shapes ofthe type described and associated metal molds into a composite moldingassembly. As used in this specification, the term "foundry shape" meansmolding shapes made of aggregate foundry mixes, such as cores and molds,and molding shapes made of other materials, such as metal shells andother metal molding parts for casting metal shapes. Shapes for moldingplastic materials also are intended to be included within the meaning ofthis term.

Such prior art uses of binder type compositions as foundry shapeadhesives have encountered various problems and have resulted in anumber of deficiencies. These problems and deficiencies includedifficult to control gel times and cure times, difficulties inapplication due to the Part I component (resin) being too viscous andthe Part II component (hardener) being too thin (overly fluid). Suchsubstantial differences in viscosities between the Part I and Part IIcomponents also result in poor mixing characteristics leading tounpredictable gel and curing times. Prior art systems also weredeficient in requiring mixing ratios between the Part I and Part IIcomponents other than 50:50, such as 60:40. Such unequal mixing ratiosbetween the parts make it difficult to maintain proper curingrelationships between the reactants at the time of application, whichagain makes for unpredictable gel and curing times and limits the typesof application equipment that can be used. A further deficiency of theprior art was that it was extremely difficult to precatalyze either ofthe components so that the catalyst had to be added as a third componentat the application site. While some precatalyzation of the resincomponent was possible, this precatalyzed resin generally had anunacceptable shelf-life (less than a one month) due to a lack ofstability of the premixed ingredients. Other deficiencies includedunworkable consistencies, foaming and other characteristics causingdimensional changes after application, low tensile strengths,resoftening with heat, deterioration of adhesive upon water absorption,and the like.

Other prior art practices include the use of relatively expensive hotmelt adhesives which are prone to thermal instability (resoftening orother loss of tensile strength) when subjected to heat from the moltenmetals being cast or other processing operations subjecting the moldingassembly to heat. Hot melt adhesives also may resoften upon core washand over drying of the parts. Such thermal instability allows the gluedparts to shift, thereby ruining the tolerances of the cast metal piece.Softening of the adhesive also may result in run out of the moltenmetal, which similarly may destroy the tolerances of the cast pieces.Run out is due to an inadequate adhesive seal between the moldingassembly parts and also may result from an improper consistency of theapplied adhesive. Another problem with hot melt adhesives is they areexpensive and hazardous to handle and the equipment used for theirapplication is subject to considerable down time and maintenance.

Prior practices also include the use of air or oven dried adhesives.This class of adhesives is slow to cure and therefore significantlylimits production rates. A delay of sometimes as much as 10 to 15 hoursafter gluing the parts of the molding assembly together may be necessarybefore molten metal can be poured into such an assembly. It has longbeen recognized that the elimination of such time delays wouldsignificantly increase production rates. In lieu of any type ofadhesive, prior art practices also include the use of metal fasteners tohold the foundry shapes together during the metal casting operation.However, such metal fasteners are expensive to provide and timeconsuming to apply. In addition to metal fasteners, weights attached tothe molding assembly were sometimes required in order to help hold theassemblied parts together during the casting process.

Although two part adhesive pastes have been used in the past, the resincomponent had an extremely high viscosity (about 50,000-60,000 cps) andthe isocyanate component had an extremely low viscosity (about 200-300cps). These very great differences in viscosities caused difficulties inmixing and application of the final adhesive composition. For example,it is very difficult to feed two components with such widely varyingviscosities through a common applicator gun and properly control themixing ratios because the viscosity differences result in substantialvariations in pumping pressures and flow rates. Prior art applicatorsystems also required auxiliary solvent flush systems to removeblockages caused by improper mixing of the hardener component and/orinterim delays in adhesive application.

DISCLOSURE OF THE INVENTION

A number of requirements have been recognized for the use of adhesivepastes in making foundry molding assemblies. These requirements includethe need for separate resin and isocyanate components each having aviscosity in the range of about 20,000 to about 50,000 centipoise (cps).The need for this consistency is that it is desirable to apply theadmixture by extrusion through a single applicator gun having a mixingchamber a short distance upstream of an outlet nozzle. A paste in thisconsistency range can be readily mixed and extruded through such anapplicator using pressures in the range of about 20 to 100 psi. Anotherrequirement is that the paste have a time period of workability (geltime) of at least two to three minutes. It also is desirable to have acure time over which the paste reaches at least 70-80% of its finaltensile strength in about 10-30 minutes after application to a foundryshape. This intermediate tensile strength preferably is in the range ofabout 100 to 150 psi, preferably at least about 125 psi.

A further requirement of a mold assembling paste is that it adhere wellboth to metal mold parts and to the foundry mix compositions used inmaking mold assembly cores. Such mold assembly cores and other partsafter adhesion to each other may be treated by dipping in a water basedsolution, and then heated to a temperature of about 275° F. for aboutone hour after assembly. Accordingly, the adhesive paste must resistbreakdown under the conditions of both such water treatment andsubsequent drying.

The present invention meets the foregoing requirements for asatisfactory adhesive paste for molding assemblies and overcomes thedeficiencies discussed above regarding prior art adhesive compositionsand other techniques for fastening together foundry shapes into acomposite molding assembly. The adhesive paste of the present inventionis a two or three part polyol resin system capable of gluing or"cementing" together foundry shapes, such as sand cores, sand molds, andmetal core and mold pieces, at room temperature. The mixed paste isapplied as a continuous "bead" or as discontinuous "spots" toappropriate surfaces of core and/or mold pieces using mixing andapplicator equipment of conventional design. The coated surfaces ofadjacent pieces are then pressed and held together until the paste"sets".

The adhesive paste is easily mixed in a one to one ratio of the resincomponent (Part I) and the isocyanate component (Part II). The mixingratio is not particularly critical since it may vary between about 45:55and about 55:45. The mixed paste remains in the form of a workableliquid for about 20% to about 60%, preferably about 40% to about 50%, ofits curing time, depending on the catalyst used. This provides workingtime for applying the paste, positioning the pieces to be assembled, andthen pressing together the pieces into the molding assembly. The gluedassembly then cures to form a thermally stable, securely bonded moldingassembly into which or around which a molten metal may be poured forcasting metal shapes.

Although it has been known heretofore that isocyanates react withphenolic resins to result in cross-linked materials, it has beendifficult to obtain cross-linked materials having acceptable properties.This has been particularly true where such mixtures of phenolic resinsand polyisocyanates are employed for gluing together foundry shapes. Inthe absence of uniform mixing of the components, the resulting moldingassemblies require long cure times, have low tensile strengths and arealso deficient in other mechanical properties. These deficiencies areovercome by the compositions of the present invention which combined theuse of particular types of polyol resins, particular polyisocyanatehardeners, particular base catalysts, particular filler materials andparticular solvent systems.

In addition to catalytic activity causing curing at room temperature,the base catalysts of the present invention add a highly surprising anddesirable property to the adhesive compositions. Most cold-curableadhesive compositions combine long gel times with long cure times orshort cure times with short gel times. The resin compositions of thepresent invention for reasons not clearly understood combine long geltimes with relatively short cure times which result in superiorapplication properties in the liquid adhesive and superior mechanicalproperties in the cured product.

The adhesive compositions of the present invention are generally madeavailable as a two-package system comprising the polyol resin componentin one package and the polyisocyanate hardener component in the otherpackage, both components being in liquid form and having relatively highviscosities. In general, the catalyst is incorporated into the resincomponent although such is not essential. At the time of use, thecontents of the two packages are combined and used in the intendedapplication. The time of workability before the composition gels (geltime) and the time required for curing will vary with the amount ofcatalyst and with the nature of the base catalyst, more particularly thepK value of the catalyst. Although the adhesive compositions of thepresent invention are particularly designed to achieve curing at roomtemperature, it is to be understood that these adhesive compositionsalso can be cured by baking at elevated temperatures.

The adhesive paste composition of the invention comprises in admixture aresin component, a hardener component, a hydrophobic filler componentand a curing agent. The resin component (Part I) includes a polyolhaving at least two hydroxyl groups and the hardener component (Part II)includes a liquid polyisocyanate having at least two isocyanate groups.The hydrophobic filler is preferably a thixotropic agent and ispreferably premixed with the hardener component. The resin componentalso preferably includes a filler which is preferably hydrophobic,although it need not be. The filler in the resin component also ispreferably a thixotropic agent.

In the two component systems described, the filler component ispreferably dispersed in both the polyol and the isocyanate components.However, the placement of the filler component in the resin component ofthe system depends on the viscosity desired for that component. Theviscosity of each component should be such that the filler does notseparate out upon prolonged standing in storage. The viscosity of boththe polyol component and the isocyanate component should be in the rangeof 7,000 to 60,000 cps, preferably 20,000 to 50,000 cps, more preferably30,000 to 40,000 cps. The stability should be such that the filler doesnot cause any adverse or premature reaction with the other constituentsof the component in which it is placed. For example, a filler thatcontains water molecules or an ingredient that reacts to produce watermolecules should not be placed in the isocyanate component sinceisocyanates undergo a cross-linking reaction with water.

Both the Part I and Part II components preferably contain as the fillercomponent a hydrophobic fumed silica which is a thixotropic agent. Theamount of this thixotropic agent blended with each part is sufficient toprovide the resin component and the hardener component with similarviscosities. The similarity in viscosities between the Part I and PartII components solves many of the problems inherent in the prior arttechnology discussed above. In addition, the relative ratio of Part I toPart II is approximately 50:50 by weight, which can vary between about55:45 and about 45:55. This means that approximately the same amount ofPart I and Part II are mixed to yield the final core paste adhesive tobe applied to foundry shapes and this greatly increases the reliabilityof the final mix with respect to its gel and curing times. Both thesimilarity of viscosities and the equal mixing of Parts I and IIcontribute to the ease of mixing and the workability of the admixture sothat conventional mixing and application equipment can be used for theadhesive paste of the invention.

Although the adhesive system can be sold as a three part system in whichthe catalyst is mixed with the Part I and Part II components at thefoundry site, the adhesive system is preferably supplied as a two partsystem in which the catalyst is premixed with the Part I component. Inthis instance, the catalyst is premixed with the Part I component at thesite of the manufacturer of the resin component. The premixed catalystis preferably a delayed action catalyst based on a strong cyclic amine,such as a blocked 1,8-diazo-bicyclo-5.4.0-undecene-7.

Accordingly, a curing agent is dissolved in the polyol component of thepreferred two part system. Alternately, the curing agent may comprise athird component separately packaged so as to be mixed simultaneouslywith both or premixed with either of the two other components just priorto application of the paste admixture to mold and/or core pieces. Inthis alternative, the catalyst may be a liquid tertiary amine or otherconventional catalyst having a relatively slow but appreciable reactionrate with the polyol alone.

The hardener component comprises liquid aliphatic, cycloaliphatic, oraromatic polyisocyanates having preferably from two to five isocyanategroups. If desired, mixtures of organic polyisocyanates can be employed.The preferred polyisocyanates are aromatic polyisocyanates, particularlya mixture of diphenyl and triphenyl polyisocyanates.

The polyol resin component may include a phenolic resin which comprisesreaction products of a phenol with an aldehyde. The aldehyde has theformula R'CHO wherein R' is a hydrogen or hydrocarbon radical of 1 to 8carbon atoms. The phenol has the general formula: ##STR2## wherein A, Band C are hydrogen atoms, or hydroxyl radicals, or hydrocarbon radicals,or oxyhydrocarbon radicals, or halogen atoms, or combinations of these.This phenol may be a multiple ring phenol such as bisphenol A. At leastabout 5 mole percent, more preferably about 5 to about 30 mole percent,of the phenol reactants employed in making the phenolic resin componentmay be a substituted phenol such as an alkyl phenol, more preferablynonyl phenol, most preferably para-nonyl phenol. The phenolic resin ispreferably non-aqueous. By "non-aqueous" is meant a phenolic resin whichcontains water in amounts of no more than about 10%, preferably no morethan about 5%, and more preferably no more than about 1% based on theweight of the resin. The phenolic resin component preferably includesbenzylic ether resins. Methylol-terminated phenolic resins also may beused.

By "phenolic resin" is meant the reaction products of a phenol with analdehyde in which the final mixture of molecules in the reactionproducts is dependent upon the specific reactants selected, the startingratio of these reactants, and the conditions of the reaction (forexample, the type of catalyst, the time and temperature of the reaction,the solvents and/or other ingredients present, and so forth). Thereaction products, that is, the phenolic resin, will be a mixture ofdifferent molecules and may contain in widely varying ratios additionproducts, condensation products, and unreacted reactants such asunreacted phenol and/or unreacted aldehyde. By "addition product" ismeant reaction products in which an organic group has been substitutedfor at least one hydrogen of a previously unreacted phenol or of acondensation product. By "condensation product" is meant reactionproducts with two or more benzene rings.

The present invention also is concerned with securing together foundrycores and molds so as to fabricate a molding assembly. Such cores and/ormolds may comprise a foundry mix containing foundry aggregate with abonding amount of up to about 10% by weight of the prior art bindercomposition described hereinabove based upon the weight of theaggregate. The foundry mix is introduced into a pattern and hardened tobecome self-supporting. The shaped foundry mix is removed from thepattern and allowed to further cure to thereby obtain a hard, solid,cured foundry shape. These foundry shapes then are secured together orto mold pieces of metal to fabricate a molding assembly.

Furthermore, the present invention is concerned with a process forcasting a metal. The process comprises fabricating a molding assembly asdiscussed hereinabove and pouring the metal while in the liquid ormolten state into or around the assembly. The metal is allowed to cooland solidify and the molded metal article is then separated from themolding assembly.

The adhesive paste of the present invention has numerous advantages overadhesive pastes of the prior art for similar applications. With respectto the present invention, the ratio of Part I to Part II can beconsistent at all times during application of the mixed adhesive to thefoundry shapes being used to assemble the molding assembly. The desiredcomposition of the admixture can be achieved very quickly upon start upof the dispensing operation due in large measure to the 50:50 ratio atwhich the Part I and Part II components can be mixed. A further featureof the invention is that the mixing ratio may vary between 45:55 and55:45 without a significant deterioration of adhesive performance. Theadhesive may be applied with a highly portable dispensing gun havingself-contained cartridges or chambers for each part, or in a dispensinggun having two flexible supply conduits for ease of movement but havingsome restrictions on portability as defined by the length of the hose orhoses providing these conduits. The dispensing gun is operable with onehand because core and mold assembling operations require foundrymen todispense adhesive with one hand while setting cores and mold pieces withthe other.

Because the viscosity of each part is approximately equal at the time ofmixing and is selected to permit ease of pumping, flow surges aresubstantially eliminated, thereby avoiding unexpected changes in mixingratios. Furthermore, the new adhesive does not require special solventflushing equipment and operations using a separate solvent component asdo certain prior art pastes. With the new adhesive system, flushing isaccomplished by continuing to dispense the Part I component aftershutting off the Part II component for a period of time sufficient toremove all Part II component from the dispensing equipment.

Another advantage of the present invention is that gel and cure timesmay be adjusted up or down according to the needs of the particular coreand mold assembling operation. This depends upon the amount and type ofcatalyst used and can be accomplished either at the point of manufactureof the adhesive system or on site at the foundry using the adhesive.Cure times may be within the range of two minutes to several hours,preferably five minutes to fifty minutes, more preferably, five minutesto fifteen minutes. Gel times during which the adhesive remains workableare about 20% to about 60% of the cure time, preferably about 40% to 50%of the cure time.

In prior art core pastes, the resin component was extremely viscouswhile the hardener component was extremely liquid. The present inventionbrings the viscosity of the hardener component and the viscosity of theresin component substantially together. The viscosity of the hardenercomponent may be in the range of 7,000 to 60,000 cps, preferably in therange of 20,000 to 50,000 cps, and more preferably in the range of30,000 to 40,000 cps. The viscosity of the resin component, as well asthe final admixture, is in the same ranges. These viscositycharacteristics of the Part I and Part II components significantlyincrease mixing efficiency and the flowability of the mixed paste duringapplication, while maintaining desirable levels of "standing power" orheight of repose after application to a surface.

Adhesive paste for foundry use must be of sufficiently high viscositywhen at rest (absence of shear) to repose high enough to ensure that theadhesive bead or spots will fully and sealingly contact the opposingsurfaces to be glued together where these surfaces are somewhat roughand uneven. The thixotropic behavior of the preferred adhesivecomposition provides a high repose or "standing" viscosity at rest forproviding a continuous seal between glued surfaces, and a substantiallylower (as much as 50% or more) viscosity under shear for ease of mixingand application. On the other hand, the at rest viscosity of the mixedadhesive paste must not be excessively high so as to hinder the blendingand mixing of the Part I and Part II components or the positioning ofthe molding assembly pieces to be joined together in close proximity.Interference with the positioning of the pieces to be joined will resultin improperly dimensioned metal castings caused by an unusually largeseparation or gap between the pieces being joined.

Unacceptable separations or gaps between the mold assembly pieces mayalso be caused by foaming or other swelling of the mixed adhesivecomposition. In this regard, there is no substantial swelling of theadhesive admixture of the present invention. In other words, the amountof swelling, if any, is not sufficient to cause appreciable separationor gaps between the mold assembly pieces or improperly dimensioned metalcastings.

Without intending to be bound by any one theory to explain the resultsachieved, it is believed that the use of a hydrophobic filler,preferably a thixotropic agent such as a chemically treated fumedsilica, in both the resin component and the hardener component providesboth of these parts with desirable viscosity characteristics withoutadversely affecting their shelf life. Similar viscosities combined withan increase in solids content and thixotropic behavior are believed toimprove both mixing and application efficiency and allows the componentsto be mixed in a 1:1 ratio by weight. The use of a delayed action cyclicamine, preferably a blocked 1,5-diazobicyclo 5,4,0 undecene 7, as thecatalyst, is believed to contribute significantly to stabilizing andincreasing the shelf life of the resin component in a two part systemwhere the resin component is precatalyzed. All of these features arebelieved to contribute to eliminating prior art problems with swellingof the applied adhesive.

The present invention therefore provides a high-performance, two-partadhesive paste for assembling foundry shapes, such as cores and molds,into molding assemblies. The strength of the adhesive bond achievedbetween the foundry shapes is sufficient to eliminate the use ofmechanical fasteners, weights and other mechanical hardware for holdingthe shapes together during the casting of liquid metal. The high tensilestrength, heat resistance, and swelling resistance of the cured adhesivepaste prevents slipping or shifting of the foundry shapes during oventreatment and metal pouring. The adhesive paste can be readily appliedas spots or beads according to the job requirements. Conventionalequipment can be used to meter, mix and apply the proper amounts ofadhesive. The equipment used in combination with the adhesive paste alsocan be easily adapted to either manual or remote control operation.

The adhesive paste of the invention is useful at or near roomtemperature (60° F.-80° F.). Accordingly, no ovens or lengthy dryingtimes are required for sufficient curing to achieve the desired tensilestrengths for handling the molding assembly. The adhesives can besupplied to the end user with differing cure times in order toaccommodate different job requirements. In this regard, highertemperatures will shorten gel and cure times while colder temperatureswill extend gel and cure times. Colder temperatures also may increaseviscosity so care must be taken not to unduly restrict flow throughpumping mechanisms and applicator conduits.

The tensile strength of the cured adhesive paste of the invention isgenerally stronger than the binder composition used to form cores andmold pieces from a sand aggregate. Thus, the molding assemblies can behandled without failure of the adhesive paste. Similarly, core and otherwashes of the foundry shapes will not adversely effect the tensilestrength of the adhesive joint. Such high tensile strengths can beachieved within minutes to fractions of an hour, depending on the curetime selected. The tensile strength is high enough to eliminate the needfor mechanical fasteners or weights. The rapid cure times availablesignificantly improve productivity of the foundry operation. Theadhesive paste will not resoften during post assembly operations such aswashing and oven drying.

Virtually all types of cores and molds can be assembled with theadhesive paste regardless of the binder used in making the cores or moldpieces from aggregate such as sand. These cores and molds can be almostof any size or shape. The molding assemblies made from these foundryshapes might include impeller core assemblies, cylinder block barrelcore assemblies, oil pump core assemblies, water jacket core assemblies,and intake manifold core assemblies for combustion engines.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood further with reference to theaccompanying drawings in which:

FIG. 1 is a bar graph illustrating gel and cure times at differentcatalyst concentrations for an adhesive paste made according to theinvention;

FIG. 2 is a graph illustrating the increase in tensile strength withtime of an adhesive composition made in accordance with the invention;

FIG. 3 is a graph illustrating the stability of the cure times providedby the extended shelf life of compositions made in accordance with theinvention; and,

FIG. 4 is a diagrammatic illustration of an applicator system forapplying the adhesive paste of the invention to foundry shapes.

BEST AND OTHER MODES FOR CARRYING OUT THE INVENTION

The adhesive paste composition of the present invention contains ahydrophobic filler material. The hydrophobic filler employed can be aninorganic or organic particulate material which has sufficienthydrophobic characteristics. By "hydrophobic" is meant that theindividual solid particles of the filler material adsorb substantiallyno water. By "substantially no water" is meant that the surface of eachparticle adsorbs less than about 1%, preferably less than about 0.75%,and more preferably less than about 0.5% of water by weight at arelative humidity of at least about 90% or greater.

A particularly important feature of the invention is that the hardenercomponent of the two component system contains a hydrophobic filler inthe amount of about 0.5% to about 20%, preferably about 1.0% to about10%, and more preferably about 1.5% to about 5%, relative to the weightof this component. A preferred hydrophobic filler is a hydrophobic fumedsilica such as CabO-Sil N-70-TS available from the Cabot Corporation ofTuscola, Illinois. Such fumed silicas may be made by the hydrolysis ofsilicon tetrachloride at about 1,100° C. so as to produce colloidalsilica particles of high purity. Such colloidal silica is generallyknown as "fumed" silica because of the high flame temperature used inthis process. By "high purity" is meant that the silica is 99% by weightsilicon dioxide with no measurable calcium, sodium or magnesium. Thesurface area of a fumed silica such as N-70-TS is about 100±20 squaremeters per gram. The fumed silica is made hydrophobic by treating itwith a compound capable of substantially decreasing its wateradsorbance. Such compounds include organosilicone compounds such assilane. A particularly preferred silane is polydimethyl siloxane. Theindividual fumed silica particles have a nominal particle size in therange of about 0.007 to about 0.012 microns.

Preferably, a filler material is also employed in the resin component ofthe two component system. Although the preferred filler for the resincomponent is a hydrophobic filler of the same type as used in thehardener component, the resin filler need not be hydrophobic. Examplesof other fillers acceptable for the resin component include ahydrophyllic fumed silica such as M-5 available from the CabotCorporation, bentonite clays preferably treated with a quaternaryammonium compound (such as SD-2 available from N. L. Industries ofHightstown, N.J.), bis-diethylene glycol terephthalates such as Terol250 and 250D, glyceryl tris 12-hydroxy stearate such as Thixcin Eavailable from N. L. Industries, polysaccharides such as Aquathixavailable from Tennneco Chemicals Company, and certain other fillerssuch as Bentone 34 available from N. L. Industries and Versamide 335available from General Mills Chemicals, Inc., of Kankakee, Ill. Theamount of filler in the admixed resin component is about 0.5% to about25%, preferably about 0.5% to about 15%, more preferably about 1% toabout 9% relative to the weight of this component.

If the filler component is all placed in either the resin component orthe hardener component, greater amounts than indicated above may have tobe provided in the single component containing the filler. It is alsopossible, of course to mix the filler with the resin component and thehardener component at the application site, in which case at least 10%,preferably about 30%, and more preferably about 40% of the filler shouldbe hydrophobic. The amount of filler added either separately or in asingle component should be sufficient to provide in the mixture anamount of filler in the range of about 0.5% to about 25%, preferablyabout 0.5% to about 15% and more preferably about 1% to about 10%,relative to the total weight of the premixed composition.

Another particularly desired characteristic of the filler is that it bea thixotropic agent. Thixotropic agents by definition impart to themixture a variable viscosity depending on the level of the shear towhich the mixture is subjected. The thixotrophy of the composition maybe measured by its thixotropic index which is the ratio of its low shearviscosity to its high shear viscosity. The thixotropic index imparted tothe composition by the thixotropic agent used should be at least about1.5, preferably at least about 2.0, as measured in the final adhesivepaste composition as ready for application to glue together foundryshapes. Certain surfactants may be added to this mixture, preferably asan ingredient in the resin (Part I) component, so as to increase thethixotropic index of the adhesive paste composition. One such surfactantis a non-ionic coupling agent containing octylphenoxy polyethoxyethanolavailable as Triton X-100 from Rohm and Haas.

The adhesive paste compositions which are benefited by use of thisinvention are known to the art and are those which contain certainpolyol resin and polyisocyanate combinations. Such polyol/isocyanateadhesive systems are admixed at or about the time of use. Typically, thepolyol and polyisocyanate ingredients of such adhesive compositions aresold, shipped and stored in separate packages (i.e., a multiple packagemolding assembly adhesive) to avoid undesirable deterioration due topremature reaction between the components. Solvents, catalysts, fillersand various optional additives are used in conjunction with theseessential ingredients, i.e., used with the polyol resin and theisocyanate.

The first component or package of the binder composition comprises anpolyol having at least two hydroxyl groups, and preferably from two tofive hydroxyl groups. If desired, mixtures of organic polyols can beemployed. Suitable polyols include polyester polyols, polyether polyols,modified polyester polyols, modified polyether polyols,phenol-formaldehyde resins, substituted phenol-formaldehyde resins,polypropylene glycols, glycols, triols, novalak resins, andmethylol-terminated phenolic resins.

The polyol resin is preferably a phenolic resin. The phenol reactantsemployed in making the phenolic resin component may include at least 5mole percent and preferably about 5 to about 30 mole percent of a alkylphenol, more preferably nonyl phenol, and most preferably paranonylphenol. The phenolic resins are substantially free of water and areorganic solvent soluble. In addition to containing nonyl phenol, thephenolic component may include any one or more of the phenols which haveheretofore been employed in the formation of phenolic resins and whichare not substituted at either the two ortho-positions or at one ortho-and the para-position, such unsubstituted positions being necessary forthe polymerization reaction. Any one, all, or none of the remainingcarbon atoms of the phenol ring can be substituted. The nature of thesubstituent can vary widely, and it is only necessary that thesubstituent not interfere in the polymerization of the aldehyde with thepnenol at the ortho- and/or para-positions. Substituted phenols that maybe employed in the formation of the phenolic resins include:alkyl-substituted phenols, aryl-substituted phenols,cyclo-alkyl-substituted phenols, alkenyl-substituted phenols,alkoxy-substituted phenols, aryloxy-substituted phenols, andhalogen-substituted phenols, the foregoing substituents containing from1 to 26 and preferably from 1 to 12 carbon atoms.

Specific examples of suitable phenols include: phenol, 2,6 xylenol,o-cresol, m-cresol, p-cresol, 3,5-xylenol, 3,4-xylenol, 2,3,4-trimethylphenol, 3-ethyl phenol, 3,5-diethyl phenol, p-butyl phenol, 3,5-dibutylphenol, p-amyl phenol, p-cyclohexyl phenol, p-octyl phenol,3,5-dicyclohexyl phenol, p-phenyl phenol, p-crotyl phenol, 3,5-dimethoxyphenol, 3,4,5-trimethoxy phenol, p-ethoxy phenol, p-butoxy phenol,3-methyl-4-methoxy phenol, and p-phenoxy phenol. Multiple ring phenols,such as bisphenol A, are also suitable. Such phenols can be described bythe general formula: ##STR3## wherein A, B, and C are hydrogen atoms, orhydroxyl radicals, or hydrocarbon radicals, or oxyhydrocarbon radicals,or halogen atoms or combinations of these. A preferred phenol componentemployed is a mixture of one or more of these phenols with nonyl phenol.

The phenol component is preferably reacted with an aldehyde to formphenolic resins, more preferably benzylic ether resins. The aldehydesreacted with the phenol can include any of the aldehydes heretoforeemployed in the formation of phenolic resins such as formaldehyde,acetaldehyde, propionaldehyde, furfuraldehyde, and benzaldehyde. Ingeneral, the aldehydes employed have the formula R'CHO wherein R' is ahydrogen or a hydrocarbon radical of 1 to 8 carbon atoms. The mostpreferred aldehyde is formaldehyde.

The methylol-terminated phenolic resins useful in the present inventionare resole resins which are organic solvent soluble. The organic solventsoluble resole resins are a well established class of resins thepreparation of which is known. However, since the resole resins having ahigh proportion of orth-ortho methylene linkages are generally theorganic solvent soluble resole resins, the majority of the resole resinsuseful in this invention are prepared from alkyl-substituted phenolswherein the para position is substituted. On the other hand, organicsolvent soluble resole resins may also be prepared from phenolsunsubstituted in the ortho and para positions by first preparing anortho-ortho novolac and then reacting the novolac with furtherformaldehyde under milder conditions to produce a methylol-terminatedresin which is an organic solvent soluble resole resin unsubstituted atthe para positions. As an illustration of this procedure, a mixture ofphenol and formaldehyde wherein the molar ratio of phenol toformaldehyde is greater than 1:1 may be condensed in the presence of anortho-ortho directing catalyst, such as sodium hydroxide, under alkalinepH, e.g., between 5 and 6, and at a temperature in the neighborhood of160° C. When essentially no free formaldehyde remains, the excess phenolis removed by vacuum distillation and the resin cooled to theneighborhood of 40° C. to 50° C. Additional formaldehyde is then addedand the subsequent exothermic reaction controlled to keep thetemperature below about 95° C. This mixture is then rapidly cooledbefore the resin becomes insoluble, which results in a methol-terminatedorganic solvent soluble resole resin having essentially no parasubstitution and being useful in this invention. The disclosures ofBritish Pat. Nos. 773,510 and 773,547 are particular pertinent to theabove resole resins prepared from phenol unsubstituted in the meta andpara positions.

A preferred class of phenolic resins that can be employed in theadhesive compositions of the present invention is described in U.S. Pat.No. 3,485,797 referred to above. The phenolic resins employed in theadhesive compositions also can include either resole or A-stage resinsor novolac resins and, when admixed with polyisocyanates and cured byuse of catalysts, these resins form adhesives of sufficient strength andother properties to be suitable in industrial applications such asgluing together the parts of a molding assembly for casting metals orplastics. The resole resins are preferred over the novolak resins. Theresitole or B-stage resins, which are a more highly polymerized form ofresole resins, are generally unsuitable. The phenolic resin employedmust be liquid or organic solvent-soluble. Solubility in organic solventis desirable to achieve uniform distribution of the components in theadhesive admixture.

The substantial absence of water in the polyol resin is desirable inview of the reactivity of the adhesive composition of the presentinvention with water. The term "non-aqueous" or substantially water-freeas employed herein is meant to define polyol resins which contains nomore than about 10 percent (10%) water, preferably no more than about 5percent (5%) water, and more preferably no more than about 1 percent(1%) water based on the weight of the resin. Mixtures of polyol resinscan be used.

The polyol resin component of the adhesive composition is, as indicatedabove, generally employed as a solution in an organic solvent. Thenature and the effect of the solvent will be more specifically describedbelow. The amount of solvent used should be sufficient to result in anadhesive composition permitting uniform coating thereof on foundryshapes and uniform reaction of the mixture. The specific solventconcentrations for the polyol resins will vary depending on the type ofpolyol resin employed and its molecular weight. In general, the solventconcentration will be in the range of up to 80 percent by weight of theresin solution and preferably in the range of about 10% to 60%, morepreferably in the range of about 15% to 40%.

The second component or package of the binder composition comprises analiphatic, cycloaliphatic, or aromatic polyisocyanate having at least 2and preferably from 2 to 5 isocyanate groups. If desired, mixtures oforganic polyisocyanates can be employed. Suitable polyisocyanatesinclude the aliphatic polyisocyanates such as hexamethylenediisocyanate, alicyclic polyisocyanates such as 4,4'-dicyclohexylmethanediisocyanate, and the dimethyl derivatives thereof. Further examples ofsuitable polyisocyanates are 1,5-naphthalene diisocyanate,triphenylmethane triisocyanate, xylene diisocyanate, and the methylderivatives thereof, polymethylenepolyphenyl isocyanates,chlorophenylene-2,4-diisocyanate, and the like.

Mixtures of isocyanates can be used. Although all polyisocyanates reactwith the polyol resin to form a cross-linked polymer structure, thepreferred polyisocyanates are aromatic polyisocyanates and particularlydiphenylmethane diisocyanate, triphenylmethane triisocyanate, andmixtures thereof, such as mondur MR and MR-200 available from MobayChemical Corporation of Pittsburgh, Penna.

The polyisocyanate is employed in sufficient concentrations to cause thecuring of the polyol resin. In general, the polyisocyanate will beemployed in a range of 10 to 500 weight percent of polyisocyanate basedon the weight of the polyol resin. Preferably, from 20 to 300 weightpercent of polyisocyanate on the same basis is employed. Thepolyisocyanate is employed in liquid form. Liquid polyisocyanates can beemployed in undiluted form. Solid or viscous polyisocyanates areemployed in the form of organic solvent solutions, the solvent beingpresent in a range of up to 80 percent by weight of the solution. Mostpreferably the isocyanate is employed in a stoichiometric amount ± about20% based on the available hydroxyl groups of the polyol resin.

The difference in the polarity between the polyisocyanates and thepolyol resins restricts the choice of solvents in which both componentsare compatible. Such compatibility is necessary to achieve completereaction and curing of the adhesive compositions of the presentinvention. Polar solvents of either the protic or aprotic type are goodsolvents for the polyol resin, but have limited compatibility with thepolyisocyanates. Aromatic solvents, although compatible with thepolyisocyanates, are less compatible with the polyol resins. Thesolvents selected must also be compatible with the filler and the curingagent.

It is therefore preferred to employ combinations of solvents andparticularly combinations of aromatic and polar solvents. Suitablearomatic solvents are benzene, toluene, xylene, ethylbenzene andmixtures thereof. Preferred aromatic solvents are mixed solvents thathave an aromatic content of at least 90 percent and a boiling pointrange of 280° to 450° F. The preferred aromatic solvents are blends suchas Hi Sol 10 and Hi Sol 15 available from the Industrial ChemicalSolvents Division of Ashland Chemical Company of Dulbin, Ohio. Suitablepolar solvents are generally those which have been classified in the artas coupling solvents and include ketones, esters, alcohols, chlorinatedhydrocarbons, glycol ethers, isophorone, 1,1,1-trichoroethane, methylenechloride, furfuryl alcohol, Cellosolve acetate, butyl Cellosolve, butylCellosolve acetate, butyl Carbitol, diacetone alcohol, and "Texanol".

Other preferred solvents include liquid dialkyl esters such as dialkylphthalate of the type disclosed in U.S. Pat. No. 3,905,934, the entirecontents of which are incorporated herein by reference. Such preferablyhave the structure: ##STR4## where R₁ and R₂ are alkyl radicals of 1 to12 carbon atoms and the total number of carbon atoms in the R groupsdoes not exceed 16. Preferably R₁ and R₂ are alkyl radicals of 3 to 6carbon atoms and the total number of carbon atoms in R₁ and R₂ isbetween 6 and 12. Thus in the above structural formula, either R groupcan be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl,isopentyl, hexyl, isohexyl, heptyl, isoheptyl, octyl, isooctyl, andother isomers of the foregoing. Particular preferred dialkyl phthalatesare dibutyl phthalate, dioctyl phthalate, dicapryl phthalate andmixtures thereof.

Other dialkyl esters include dimethyl glutarate such as available fromDuPont under the trade designation DBE-5, dimethyl adipate availablefrom DuPont under the trade designation DBE-6, dimethyl succinate,dioctyl adipate, and mixtures of such esters which are available fromDuPont under the trade designation DBE, and dialkyl adipates andsuccinates with alcohols up to 12 carbon atoms. Particularly preferredsolvent systems are mixtures of dimethyl succinate, dimethyl glutarateand dimethyl adipate such as DBE and DBE-2. DBE is about 10% to about25% dimethyl adipate, about 45% to about 65% dimethyl gluterate andabout 20% to about 30% dimethyl succinate. DBE-2 is about 20% to about35% dimethyl adipate, about 65% to about 80% dimethyl gluterate, and upto 3% maximum of dimethyl succinate.

Although three-package systems are contemplated, the binder compositionsare preferably to be made available as a two-package system with thepolyol resin and curing agent in one package and the isocyanatecomponent in the other package. Broadly described, the adhesivecompositions of the present invention comprise organic solvent solublepolyol resins, which may contain benzylic ether structure and/ormethylol end groups in non-aqueous systems which have been combined withsufficient polyisocyanate to cross-link the polyol resin and whichcontain as the curing catalyst a base having a pK value in the range ofabout 7 to about 12 as determined in a known manner. The determinationof pK values of organic compounds may be made in various conventionalmanners depending upon the nature of the particular organic compound.The pK values of compounds useful as catalysts in this invention may bedetermined according to methods described by D. D. Perrin inDissociation Constants of Organic Bases in Aqueous Solution(Butterworths, London 1965).

The pK value is the negative logarithm of the dissociation constant ofthe base and is a well-known measure of the basicity of a basicmaterial. The higher this number is, the weaker the base. The basesfalling within this range are generally organic compounds containing oneor more nitrogen atoms. In view of the varying catalytic activity andvarying catalytic effect desired, catalyst concentrations will varywidely. In general, the lower the pK value is, the shorter will be thegel and curing times of the paste composition and the faster, morecomplete will be the cure. Any acidity present in added ingredients suchas solvents may affect the catalytic activity. In general, however,catalyst concentrations will range from 0.01% to 10% by weight of thepolyol resin.

The catalyst materials include compounds containing at least onenitrogen atom in the ring structure. Specific examples of bases whichhave pK values within the necessary range include 4-alkyl pyridineswherein the alkyl groups has from one to four carbon atoms,isoquinoline, arylpyridines such as phenyl pyridine, pyridine, acridine,2-methoxpyridine, pyridazine, 3-chloro pyrindein, quinoline, N-methylimidazole, 4,4-dipyridine, phenyl-propyl pyridine,1-methylbenzimidazole, and 1,4-thiazine.

Other suitable catalysts include liquid tertiary amines such as triethylamine, Polycat 77 (available from the Chemical and Agricultural ProductsDivision, Abbott Laboratories, North Chicago, Ill.), liquid diaminessuch as ethylene diamine and triethylene diamine, morpholines such asN-methyl and N-ethyl morpholine, oleic and formic acid of DMATA, and1,5-diazabicyclo 5,4,0 undecene 7 (DBU). Particular preferred catalystsfor premixing with the resin component (Part I) are blocked DBUcompounds such as DBU blocked with formic acid (Polycat 610/50),phenolic acid (Polycat SA-1), and 2-ethylhexanoic acid (Polycat SA-102).

The Polycat catalysts referred to are all available from AbbottLaboratories.

All of the foregoing catalysts, either alone or in mixtures thereof, maybe mixed with the other components of the adhesive paste composition atthe application site. Catalyst concentrations can be in the range ofabout 0.01% to about 15%, preferably about 1.0% to about 7.0% relativeto the weight of the resin component. Where the catalyst is premixedwith the resin component away from the application site, itsconcentration can be in the range of about 0.1% to about 15%, preferablyabout 0.1% to about 5.0% relative to the weight of the premixed resincomponent.

In preparing application site mixtures, the catalyst preferably is firstmixed with the resin component, although it can be mixed first with thehardener component or added separately as a third component to aprevious or simultaneous mix of the resin and hardener components. Forthe preparation of a precatalyzed resin component away from theapplication site, such as at the plant of the manufacturer of a twocomponent system, the catalyst is preferably a blocked DBU. Althoughother catalyst may be used for precatalyzation of the resin componentaway from the application site, these compositions may have asignificantly shorter shelf life ranging from a few hours to severalweeks. For example, an unblocked amine catalyst in a prior art pastecomposition decreased the curing time by as much as 46% in three weeksas shown by line 11 in FIG. 3. In addition to the change in curing timewith aging, this composition also exhibited significant foamingcharacteristics which made the composition undesirable within a fewweeks after admixture of the catalyst with the resin component. Suchfoaming may adversely affect the dimensional stability of the moldingassembly. In comparison, the composition of the present invention with ablocked DBU catalyst has a stable shelf life of over four months asdetermined by an absence of foaming and no significant change in curingtime as shown by lines 12, 14, 16 and 18 of FIG. 3 and by the datapresented in Table I. Another important characteristic of the presentinvention is that the gel, set and cure times of the final admixture canbe controllably varied over a significant range by selecting acorresponding catalyst concentration as shown in the bar chart of FIG. 1and the data presented in Table II. The gel time is preferably about 40%to 60% of the set time, more preferably about 50%. By "set" time ismeant the time required for the composition to reach a fully hardenedstate in a laboratory cup. The new paste composition also rapidlyachieves full cure strength as determined by the tensile strength of thepaste holding two sand foundry shapes (dog bones) together exceeding thestrength of the cured foundry shape binder. By "cure" time is meant thetime required to achieve this tensile strength. As shown in column 3 ofTable II, final cure strength is achieved within a time period that isonly about a factor of 4 to 8 greater than the gel time. This is alsoshown in FIG. 1 as represented by the bar graph designated as @70° F.".

In foundry mix compositions for making foundry shapes of the type usedin making molding assemblies, the aggregate constitutes the majorconstituent and the binder constitutes a relatively minor amount. Inordinary sand type foundry applications, the amount of binder isgenerally no greater than about 10% by weight and frequently within therange of about 0.5 to about 7% by weight based upon the weight of theaggregate. Most often, the binder content ranges from about 0.6 to about5% by weight based upon the weight of the aggregate in ordinary sandtype foundry shapes. For casting of low melting point metals whereshake-out and collapsibility are important, about 0.6 to about 1.5% byweight based upon the weight of the aggregate in ordinary sand typefoundry shapes is preferably used.

                                      TABLE I                                     __________________________________________________________________________                 Ratio                                                                    PART I                                                                             50%                                                                      PART II                                                                            50%                                                                           .1% SA-1 Catalyst (precatalyzed)                                         Made 1/25/85                                                          % Catalyst                                                                          Test Date                                                                           Gel Time                                                                           Set Time                                                                           Comments                                                __________________________________________________________________________    .1% SA-1                                                                            1/29/85                                                                             21/2'                                                                              6'   (a) Glue joint stronger than                                                  dog bone                                                                      (b) No foaming*                                                               (c) Easy mixing                                                               (d) Good standing power                                 .1% SA-1                                                                            2/15/85                                                                             2'45"                                                                              5'45"-                                                                             No foaming, others also same                                             6'30"                                                                              as above                                                                 (hard to                                                                      tell)                                                        .1% SA-1                                                                            2/26/85                                                                             2'45-3'                                                                            51/2-61/2                                                                          No foaming, same as above                                                (hard to                                                                      tell)                                                                    Definitely brittle                                                            hard @ 7'                                                         .1% SA-1                                                                            4/4/85                                                                              31/2'                                                                              5'45"                                                                              No foaming, same as above                               __________________________________________________________________________     *Note: Old composition foams after 25 days, which changes dimensional         stability of molds.                                                      

                                      TABLE II                                    __________________________________________________________________________    GEL TIMES OF NEW 50:50 RATIO CORE PASTE COMPONENTS (ALL APPROX. VALUES)       Col. 1                                                                        Cup gel test using Part I @ 90-100° F. (directly                                                              Col. 3                                 after making the Part I in lab mixer)  w/Part I @ 70° F. then                                                 glue                                   Total amount of Part I and II = 36 grams for test                                                     Col. 2         dog bones (@ 70° F.)                                                   together                               15 seconds stirring time in cup                                                                       w/Part I @ 70° F.                                                                     and set until stronger                 % SA-1 Amine                                                                           Gel Time                                                                             Set Time                                                                              Gel Time                                                                             Set Time                                                                              than core                              __________________________________________________________________________    .5       20 sec.                                                                              40 sec. 30-35 sec.                                                                           50-55 sec.                                                                            2 min.                                 .4       30 sec.                                                                              50 sec. 40 sec.                                                                              1 min., 15 sec.                                                                       3 min.                                 .32      30-40 sec.                                                                           1 min.  50 sec.                                                                              1 min., 40 sec.                                                                       4 min.                                 .21      1 min. 2 min.  1 min., 20 sec.                                                                      2 min., 25 sec.                                                                       6-7 min.                               .12      1 min., 35 sec.                                                                      3 min., 45 sec.                                                                       2 min., 20 sec.                                                                      4 min., 10 sec.                                                                       13 min.                                .09      2 min., 20 sec.                                                                      5 min., 45 sec.                                                                       3 min. 6 min., 30 sec.                                                                       20 min.                                .05      4 min. ≈10 min.                                                                      5 min. 11 min., 30 sec.                                                                      35-40 min.                             __________________________________________________________________________

In molds and cores for precision casting applications, the amount ofbinder is not substantially greater than about 40% by weight andfrequently within the range of about 5 to about 20% by weight based uponthe weight of the aggregate. When preparing a foundry shape forprecision casting, the predominant portion and generally at least about80% of the aggregate has an average particle size no larger than 150mesh (Tyler Screen Mesh) and preferably between about 325 mesh and 200mesh (Tyler Screen Mesh). Preferably at least about 90% by weight of theaggregate for precision casting applications has a particle size nolarger than 150 mesh and preferably between 325 mesh and 200 mesh. Thepreferred aggregates employed for precision casting applications arefused quartz, zircon sands, magnesium silicate sands such as olivine,and aluminosilicate sands.

Although the aggregate employed is preferably dry, moisture of up toabout 1 weight percent based on the weight of the aggregate can betolerated. This is particularly true if the solvent employed isnon-water-miscible or if an excess of the polyisocyanate necessary forcuring is employed, since such excess polyisocyanate will react with thewater.

The foundry mix is molded into the desired shape, whereupon it can becured so as to retain this shape upon removal from the mold. Curing canbe affected by passing a gaseous tertiary amine, such as triethylamineor dimethylethyl amine, through the molded mix as described in U.S. Pat.No. 3,409,579.

The foregoing foundry binder system is best known as the "cold box"process. The adhesive paste of the present invention provides excellentbonding betweening foundry shapes made from such foundry mixcompositions and between such foundry shapes and associated metal partsof molding assemblies. Without any intention of being bound by any onetheory, it is believed that the adhesive paste adhesion may be enhancedby penetration of the paste into the bound aggregate of the foundryshapes and possibly some crosslinking by residual activity of bindermolecules having reactive groups similar to those of the pastecomposition. However, the new adhesive paste composition also providesexcellent adhesion for foundry shapes utilizing other foundry bindersystems, such as the hot box process, the warm box process, the no-bakeprocess, the core oil process, and the shell process.

In order to further understand the present invention, the followingnon-limiting examples concerned with adhesive pastes for gluing togetherfoundry shapes are provided. In these examples and throughout thisspecification, all parts and percentages are by weight unless thecontrary is stated.

EXAMPLE 1

The following is illustrative of a typical procedure which can beemployed to prepare phenolic resins suitable for use in accordance withthe present invention.

To a clean reactor purged with inert gas charge 63.35 parts of a 99%synthetic phenol and 36.41 parts of flake paraformaldehyde whilemaintaining an inert gas blanket. With the reactor condensor set forreflux and with the reactor agitator on, charge 0.24 parts of a leadcatalyst known as Cem-All which is a blend of solvents and syntheticacids containing about 24% lead by weight in a catalyst compositionavailable from Mooney Chemicals, Inc., of Cleveland, Ohio. Afterobtaining a uniform mixture, turn off the inert gas blanket and heat thereactor to 227° F. to 230° F. (108° C. to 110° C.), maintaining a rateof temperature increase so as to attain this temperature inapproximately 1 to 11/2 hours. After this temperature is attained, it isheld for about 30 minutes while the batch exhibits a mild exotherm.Cooling water may be required to control the batch temperature withinthe 227° F. to 230° F. range. The temperature should not be allowed todrop below 227° F. during this period as this might cause a loss of theexotherm. After 30 minutes at 227° F. to 230° F., allow the temperatureof the batch to rise to 230° F. to 237° F. (112° C. to 114° C.) and holdthe temperature in this range for about 60 minutes. Some cooling watermay still be required during this period. At the end of this 60 minuteholding period, the resin should be clear indicating completedissolution of the paraformaldehyde. If this not the case, processingshould be discontinued because an unclear resin indicates a paraformquality problem or a potentially dangerous overcharge situation.

After 60 minutes at 230° F. to 237° F. and having observed a clearresin, the condensor should be set to distill to a receiver and adequateheat should be applied to raise the temperature of the batch to 257° F.to 259° F. (125° C. to 126° C.). This batch temperature range should beachieved within a 45 to 60 minute period. This is a dehydration step andthe batch must be held within the specified range throughoutdehydration. At 250° F. during the upheat period, the reactor, condensorand receiver should be sealed. A first refractive index determinationshould then be made as soon as the batch reaches 250° F., but no morethan 60 minutes after the time at which heat was applied at thebeginning of the upheat step when the batch was at 235° F. Therefractive index is recorded at 15 minute intervals until a test of1.5800 is obtained. Sample intervals are then decreased to 5 minuteperiods until the batch reaches a refractive index of 1.5940.

At a refractive index of 1.5940, full cooling and vacuum is applied tothe reactor as rapidly as possible and sampling is continued at 2 minuteintervals until a refractive index end point of 1.5990 is obtained. Thisvacuum step may take less than 5 minutes to achieve the desired endpoint. At the end point of 1.5990, the vacuum is immediately releasedand cooling is continued as rapidly as possible until a temperature of220° F. maximum is achieved. The batch is then pumped to a mixing vesselfor solvent addition, after which the phenolic resin is suitable for useas the Part I component of the present invention.

EXAMPLE 2

The following is illustrative of a typical procedure which can beemployed to prepare a two package system in accordance with the presentinvention. 40 to 60 parts of the resin component of Example 1 are heatedto about 220° F. and mixed with 40 to 60 parts of a solvent such asHiSol 15 (available from Ashland Chemical Company with a boiling pointrange of 182° C.-204° C.), DBE or DBE-2. The resin and solvent may beblended in a standard laboratory mixing tank. The solvated resin is thenblended in a standard laboratory mixer, such as a Hobart N-50 from theHobart Corporation, of Columbus, Ohio, with 0.5 to 25 parts of a fillercomponent, such as Cab-O-Sil N-70-TS fumed silica, and with 0.01% to10.0% by weight of a premix catalyst, such as Polycat SA-1 or PolycatSA-102 (a blocked DBU compound). Blending is continued until asubstantially uniform mixture is obtained. To this mixture also may beadded a surfactant such as 0.01% to 1.0% by weight of Triton X-100. Thiscomposition is then packaged as Part I of the two part adhesive pastesystem.

The Part II component is prepared by blending in a Hobart N-50 mixerabout 80% to about 99.9% by weight of Mondur MR 200 with about 0.1% toabout 20% by weight of a hydrophobic filler, preferably a thixotropicagent such as Cab-O-Sil N-70-TS fumed silica. This mixture is thenpackaged as the Part II component of the adhesive paste composition ofthe invention.

The above Part I and Part II components are preferably mixedsimultaneously with their application to foundry shapes by conventionalmixing and applicator gun equipment. Equipment designed for preparationof liquid silicone rubber may readily be adapted for mixing andapplication of the adhesive paste of the invention. One such mixingassembly is a model S4-5 meter-mix machine with a model 12004-Xapplicator gun available from Fluid Automation, Inc., of Wixom, Mich.Another meter, mix and dispense machine usable with the invention is thePosiratio Machine with a hand held Posimixer applicator gun availablefrom Liquid Control Corporation of North Canton, Ohio. A completelyportable applicator system for mixing and applying the adhesive paste ofthe invention is a high pressure dispense gun utilizing a singlecartridge with two separate chambers, one for the resin component andthe other for the hardener component, and having a mixing tubedownstream of these two chambers. One such dispensing gun is theSupermix II also available from Liquid Control Corporation.

EXAMPLE 3

The following is a specific example of the preparation of a two packagesystem in accordance with the present invention. 80 parts of the resincomponent of Example 1 are heated to about 220° F. and preblended bymixing with 7.75 parts of DBE and 12.25 parts of HiSol 10. The resin andsolvent are blended in a standard laboratory mixing vessel until theresin is dissolved. 96 parts of this preblend is then blended in astandard laboratory mixer, such as the Hobart N-50, with 2.5 parts of ahydrophillic silica known as M-5 from the Cabot Corporation, 1.5 partsof DBE and 0.35 parts of Polycat SA-1 (a blocked DBU compound). Blendingis continued until a substantially uniform mixture is obtained. Thiscomposition is then packaged as Part I of the two part adhesive pastesystem.

The Part II component is prepared by blending in a Hobart N-50 mixer 96parts by weight of Mondur MR 200 with 4 parts of a hydrophobicthixotropic agent known as Cab-O-Sil N-70-TS fumed silica available fromCabot Corporation. This mixture is then packaged as the Part IIcomponent of the adhesive paste composition of the invention.

Upon mixing the Part I and Part II components, good mixing was obtainedbut the resulting mixture was considered to be too flowable prior togel. Upon further curing, a hard gel was obtained which did not swell.

EXAMPLE 4

Example 3 is repeated except the M-5 filler is replaced by 2.5 parts ofCab-O-Sil N-70-TS. The characteristics of the admixture of Parts I andII were substantially the same as Example 3 except that the reactivity,i.e., the curing time, was somewhat faster.

EXAMPLE 5

Example 3 is repeated except that the preblend is mixed with 4.5 partsinstead of 1.5 parts of DBE. The characteristics of the admixture ofParts I and II were substantially the same as Example 4 except thatflowability was improved prior to gel.

EXAMPLE 6

Example 3 was repeated except the M-5 filler of the resin component wasreplaced by 2.5 parts of Cab-O-Sil N-70-TS, and the N-70-TS fillercomponent of the hardener was replaced by 3 parts of the M-5 filler andthe amount of MR-200 increased to 97 parts. The flowability of themixture of Parts I and II was considered to be excessive in that it didnot have sufficient standing power and was too fluid to provide a goodseal between mating parts.

EXAMPLE 7

Example 3 is repeated except in the resin component the M-5 filler isreplaced by 3 parts of the N-70-TS filler, the amount of DBE changedfrom 1.5 to 1 part and the amount of SA-1 changed from 0.35 to 0.3parts. In the hardener component, the MR-200 component was increased to96.5 parts and the N-70-TS was lowered to 3.5 parts. In this embodiment,both Part I and the Part II had similar viscosities and excellent mixingcharacteristics. The at rest repose (no shear) and the applicationviscosity (shear) of the mixture was also excellent. However, the settime was relatively fast, being from 1 to 2 minutes.

EXAMPLE 8

Example 7 is repeated except the amount of premixed catalyst in theresin component was reduced to 0.25 parts of SA-1. The mixing, reposeand application characteristics remained excellent, and the set time wasabout the same as in Example 7.

EXAMPLE 9

Example 7 was again repeated except the amount of catalyst was reducedto about 0.15% SA-1. This amount of catalyst did not significantlychange the characteristics of the Example 7 composition.

EXAMPLE 10

Example 7 was again repeated except that the amount of catalyst wasreduced to 0.10 parts SA-1. This provided a somewhat slower set time ofabout 21/2 to 3 minutes.

EXAMPLE 11

Example 7 was again repeated except the amount of catalyst in the resincomponent was reduced to 0.15 parts SA-1 and the amount of filler in thehardener component was increased to 4 parts of N-70-TS. This provided asubstantially slower set time relative to Example 7 of about 4 minutes.

EXAMPLE 12

Example 11 was repeated except that the amount of filler in the hardenercomponent was increased to 5 parts N-70-TS. This change resulted in aneven slower gel time of about 6 minutes and a set time of about 11minutes.

EXAMPLE 13

Example 7 was repeated except that the amount of catalyst in the resincomponent was reduced to 0.06 parts. The gel time of the mixture wassomewhat slower, being about 21/2 minutes. The composition becamerubbery at 4 minutes and hard at 8 minutes (set time) when applied to adog bone test sample made from a foundry mix. This composition cured onthe dog bone sample at about 20.5 minutes. The composition exhibited thesame excellent mixing and application characteristics of the compositionof Example 7.

EXAMPLE 14

Example 13 was repeated except that the amount of filler in the hardenercomponent was increased to 5 parts N-70-TS. This composition had a geltime of 9.5 minutes, became rubbery at about 25 minutes and hard atabout 75 minutes on a dog bone sample. This composition cured on the dogbone sample after about 21/2 hours.

EXAMPLES 15-22

In these examples, a preblend for the resin component was prepared inthe same manner as in Example 3 except that it contained 79.38 parts ofthe phenolic resin of Example 1, 7.68 parts of DBE and 12.94 parts ofHiSol 15. 97 parts of this preblend were then blended with 3 parts ofCab-O-Sil N-70-TS. To this resin component was added different amountsof SA-1 catalyst as specified along the Y-axis of FIG. 1. The resincomponent was made up of 97 parts MR-200 and 3 parts of Cab-O-SilN-70-TS. The resin and hardener components had similar viscosities andwere readily mixed to provide an adhesive paste having excellentpumping, application and repose characteristics. The composition curedto a hard gel and exhibited no swelling. The gel time, set time andcuring time on dog bones of this composition were tested and the resultsof these tests are illustrated in FIG. 1.

EXAMPLE 23

In this example, 100 grams of a phenolic resin available from AshlandChemical Company as Pepset 1600 were mixed with 0.35 grams of SA-1 toprovide a resin component. 100 grams of MR-200 and 5 grams of N-70-TSwere mixed to provide a hardener component. These Part I and Part IIcomponents were then mixed to provide an adhesive paste in accordancewith the present invention. This paste composition had good gelcharacteristics but a fairly low viscosity.

EXAMPLE 24

Example 23 was repeated except 2 grams of Cab-O-Sil N-70-TS filler wereadded to the resin component. This improved both the gel time and theviscosity characteristics of the Example 23 composition.

EXAMPLE 25

A preblend for the resin component was made up of 85 parts Pepset 1600and 15 parts of a solvent available as EBPA. 96 grams of this preblendwere mixed with 4 grams of Cab-O-Sil N-70-TS and 0.35 grams of SA-1 toprovide the resin component. The hardener component was made up of 98parts of MR-200 and 2 parts of N-70-TS. These Part I and Part IIcomponents had excellent mixing and application characteristics andprovided a good gel time. This composition provided a rubbery gel.

EXAMPLE 26

In all of the above examples, the invention was utilized as a 2 partadhesive system. The invention also may be utilized as a 3 part adhesivesystem to be mixed at the application site. In this application, 0.01%to 10% of the catalyst may be preblended in either the Part I or thePart II component, although the catalyst is preferably preblended withthe resin component even where such preblending is used at theapplication site.

The curing agent need not be preblended with either the resin or thehardener component, but the 3 components may be mixed simultaneously ina batch type applicator or in an applicator gun having 3 separate linesfeeding into a unitary mixing chamber. In a 3 lines mixing gun, thecatalyst is preferably added at the last downstream inlet near the pointof discharge of the dispensing gun. In this application, the resincomponent (Part I) is placed in 1 feed container, the hardener component(Part II) is placed in a second feed container and the catalyst (PartIII) is placed in a third feed container. All of these components arethoroughly mixed mechanically in the static mixing tube or chamber ofthe dispensing gun. Alternatively, these three components may be addedto a common flexible plastic bag, kneaded to affect a uniform mixing,and squeezed through a applicator nozzle of this bag type applicator.

An illustrative example of a three part adhesive system for applicationto foundry shapes is as follows with the mixing of the three componentsbeing controlled by mixing ratios: 70 to 30 parts, preferably 55 to 45parts, of Part I are mixed with 30 to 70 parts, preferbly 45 to 55parts, of Part II and with 0.01 to 10 parts, preferably 0.05 to 5 parts,of Part III.

The adhesive paste admixture is applied to foundry shapes as acontinuous bead or as discontinuous spots or dabs. The coated surfacesof the foundry shapes are then pressed together while the adhesive pasteis still workable (within the gel time) and then set aside or heldtogether until the paste "sets", namely, until it has hardenedsufficiently to provide such tensile strength that accidental vibrationor movement of the molding assembly will not cause dislocation of itsparts. Depending on the amount of curing agent (Part III) used, the settime of the paste composition may be varied from about 15 seconds toabout 2 hours. An important feature of the invention is that the pastecomposition remains workable up until its gel time, which may be up to60% of the overall set time. Once the paste gels, it is no longerworkable and the adhered parts of the molding assembly should not bemoved until at least 70% or 80% of the tensile strength of the curedpaste has been achieved.

What is claimed is:
 1. An adhesive paste comprising in admixture a resincomponent, a hardener component, a filler component and a curing agent,said resin component including a polyol having at least two hydroxylgroups, said hardener component including a liquid polyisocyanatecontaining at least two isocyanate groups, said curing agent comprisinga base, and said filler component comprising a hydrophobic fillermaterial which is a thixotropic agent, such that the relative weightratio of resin component to hardener component is from 45:55 to 55:45,the relative weight ratio of curing agent to resin component is from0.01:99:99 to 15:85, and the relative weight ratio of the hydrophobicfiller to hardener component is from 0.5:99.5 to 20:80.
 2. Thecomposition of claim 1 in which said admixture is made by mixingtogether a premixed resin component and a premixed hardener component.3. The composition of claim 2 in which said premixed hardener componentcontains said hydrophobic filler.
 4. The composition of claim 3 in whichsaid premixed resin component contains a filler.
 5. The composition ofclaim 4 in which said premixed resin component contains a hydrophobicfiller.
 6. The composition of claim 5 in which the hydrophobic filler insaid resin component, the hydrophobic filler in said hardener component,or both said resin filler and said hardener filler are thixotropicagents.
 7. The composition of claim 4 in which the filler in said resincomponent, the hydrophobic filler in said hardener component, or bothsaid resin filler and said hardener filler are thixotropic agents. 8.The composition of claim 1 in which the amount of said filler is about0.5% to about 25% relative to the weight of said composition.
 9. Thecomposition of claim 1 in which the amount of said filler is about 0.5%to about 15% relative to the weight of said composition.
 10. Thecomposition of claim 1 in which the amount of said filler is about 1.0%to about 10% relative to the weight of said composition.
 11. Thecomposition of claim 3 in which the amount of said hydrophobic filler insaid premixed hardener component is about 0.5% to about 20% relative tothe weight of said premixed hardener component.
 12. The composition ofclaim 3 in which said hydrophobic filler is a thixotropic agent and theamount of said hydrophobic filler in said premixed hardener component isabout 1.0% to about 10% relative to the weight of said premixed hardenercomponent.
 13. The composition of claim 12 in which the amount of saidhydrophobic filler in said premixed hardener component is about 1.5% toabout 5% relative to the we:ght of said premixed hardener component. 14.The composition of claim 4 in which the amount of said filler in saidpremixed resin component is about 0.5% to about 25% relative to theweight of said premixed resin component.
 15. The composition of claim 14in which the filler in said premixed resin component is a thixotropicagent and the amount of said filler in said premixed resin component isabout 0.5% to about 15% relative to the weight of said premixed resincomponent.
 16. The composition of claim 15 in which said resin filler ishydrophobic and the amount of said filler in said premixed resincomponent is about 1.0% to about 9% relative to the weight of saidpremixed resin component.
 17. The composition of claim 1 in which saidfiller comprises silica.
 18. The composition of claim 17 in which saidsilica is treated with another compound to make it hydrophobic.
 19. Thecomposition of claim 18 in which said silica is a fumed silica and saidtreating compound is an organosilicon compound.
 20. The composition ofclaim 19 in which said organosilicon compound is a silane.
 21. Thecomposition of claim 19 in which said organosilicon compound is apolydimethyl siloxane.
 22. The composition of claim 1 in which said basehas a pK value in the range of about 7 to about
 12. 23. The compositionof claim 22 in which said base is an organic nitrogen compound.
 24. Thecomposition of claim 22 in which said base is a heterocyclic nitrogencompound.
 25. The composition of claim 22 in which said base is pyridineor a derivative of pyridine.
 26. The composition of claim 22 in whichsaid base is 4-alkyl pyridine wherein the alkyl group has from one tofour carbon atoms, isoquinoline, an aryl-pyridine, acridine, 2-methoxypyridine 4,4-dipyridine, phenylpropyl pyridine, or a mixture thereof.27. The composition of claim 1 in which said curing agent is a liquidtertiary amine.
 28. The composition of claim 1 in which said curingagent is the amine 1,8-diaza-bicyclo-5,4,0-undecene-7.
 29. Thecomposition of claim 28 in which said amine is blocked.
 30. Thecomposition of claim 29 in which said amine is blocked with an organicacid.
 31. The composition of claim 30 in which said amine is blockedwith a phenolic acid, a 2-ethylhexanoic acid, formic acid, or a mixturethereof.
 32. The composition of claim 22 in which the amount of saidbase is about 0.01% to about 15% relative to the weight of the resincomponent.
 33. The composition of claim 22 in which the amount of saidbase is about 1.0% to about 7.0% relative to the weight of said resincomponent.
 34. The composition of claim 2 in which said curing agent isin said premixed resin component in an amount of about 0.01% to about15% relative to the weight of said premixed resin component.
 35. Thecomposition of claim 34 in which the amount of said curing agent in saidpremixed resin component is about 0.05% to about 5.0% relative to theweight of said premixed resin component.
 36. The composition of claim 1in which the resin component includes polyester polyols, polyetherpolyols, phenol-formaldehyde resins, glycols and triols.
 37. Thecomposition of claim 1 in which said resin component includes a phenolicresin which comprises reaction products of a phenol and an aldehyde,said phenol having the general formula: ##STR5## wherein, A, B and C arehydrogen atoms, or hydroxyl radicals, or hydrocarbon radicals, orhalogen atoms, or combinations of these, and said aldehyde having thegeneral formula R'CHO, wherein R' is a hydrogen or a hydrocarbon radicalof 1 to 8 carbon atoms.
 38. The composition of claim 1 in which saidpolyisocyanate includes hexamethylene diisocyanate, alicyclicpolyisocyanates such as 4,4'-dicyclohexylmethane diisocyanate, and thedimethyl derivatives thereof, 1,5-naphthalene diisocyanate,triphenylmethane triisocyanate, xylene diisocyanate, and the methylderivatives thereof, polymethylenepolyphenyl isocyanates,chlorophenylene-2,4-diisocyanate or mixtures thereof.
 39. Thecomposition of claim 1 in which said polyisocyanate includes an aromaticpolyisocyanate.
 40. The composition of claim 39 in which said aromaticpolyisocyanate includes diphenylmethane diisocyanate, triphenyl methanetriisocyanate, or mixtures of said diisocyanate and said triisocyanate.41. The composition of claim 1 which further comprises an organicsolvent comprising an aromatic solvent, a polar solvent, or a mixture ofan aromatic solvent and a polar solvent.
 42. The composition of claim 41in which said aromatic solvent is a mixture of solvents having anaromatic content of at least about 90% and a boiling point range ofabout 280° F. to 450° F.
 43. The composition of claim 41 in which saidpolar solvent includes ketones, esters, alcohols, chlorinatedhydrocarbons, glycol esters, or mixtures thereof.
 44. The composition ofclaim 41 in which said polar solvent includes furfuryl alcohol,Cellosolve acetate, butyl Cellosolve, butyl Cellosolve acetate, butylCarbitol, diacetone alcohol, dimethyl adipate, dimethyl glutarate,dimethyl succinate, isophorone, dioctyl adipate, 1,1,1-trichloroethane,methylene chloride, dibutyl phthalate, dioctyl phthalate, dicaprylphthalate, or mixtures thereof.
 45. The paste of claim 1 in which, afteradmixture, said paste is a workable liquid for about 20 percent to 60percent of its cure time.
 46. The paste of claim 1 wherein the viscosityof the paste under shear is as much as 50 percent or more lower than thestanding viscosity.
 47. The paste of claim 2 wherein sufficienthydrophobic filler is used to provide both the premixed resin componentand the premixed hardener component with a viscosity in the range of7,000 cps and 60,000 cps at 60° F. to 80° F. prior to admixture of saidpremixed components.
 48. The paste of claim 2 wherein sufficienthydrophobic filler is used to provide both the premixed resin componentand the premixed hardener component with a viscosity in the range of20,000 cps and 50,000 cps at 60° F. to 80° F. prior to admixture of saidpremixed components.
 49. The paste of claim 1 wherein said paste iscurable at room temperature so as to set within a period of time afteradmixture of about two hours or less.